Various methods and apparatus are known for purifying solvents, particularly water. One such method utilizes the principle of reverse osmosis to reduce or eliminate the quantity of dissolved solids in a liquid. According to the reverse osmosis principle, a semi-permeable membrane is used to separate the solvent from the dissolved solids. For example, in purifying water, a membrane is selected that exhibits greater permeability to water than the dissolved solids carried by the water. Raw feed water is applied to the membrane at a pressure generally greater than the osmostic pressure of the water. Under pressure, water passes through the membrane leaving behind the dissolved solids. The liquid passing through the membrane is generally termed “permeate” whereas the liquid remaining on the input side of the membrane is generally termed “concentrate” and is usually discarded to a drain.
Since the concentration of the solutes increases on the concentrate side of the membrane during the reverse osmosis process precipitation of one or more of the dissolved solids can occur. This precipitation can cause plugging of the membrane, thereby lowering the efficiency of the process. To remedy this, some systems recycle a portion of the permeate back through the membrane to flush the membrane of these precipitates. One such example of a conventional fluid treatment system using a permeate flush is illustrated in U.S. Pat. No. 4,629,568 entitled “Fluid Treatment System” to Ellis III, which is herein incorporated by reference and attached hereto as an appendix.
Due to the number of products and byproducts generated by the reverse osmosis process, as well as the need to periodically flush the membrane, conventional fluid treatment systems require a multitude of plumbing connections and space to accommodate all the necessary processing and storage components. Such systems are therefore susceptible to leaks and require a large amount of space. There is therefore a need to provide a fluid treatment system that is capable of performing all the aforementioned tasks while minimizing the probability of leakage and requiring a minimal amount of space.